Multi-parameter adaptive loop filtering in video processing

Abstract

Devices, systems and methods for video processing are described. In an exemplary aspect, a method for video processing includes performing a conversion between a coded representation of a video comprising one or more video regions and the video. The coded representation includes first side information that provides a clipping parameter for filtering a reconstruction of a video unit of a video region using a non-linear adaptive loop filter, and wherein the first side information is signaled together with second side information indicative of filter coefficients used in the non-linear adaptive loop filter.

What is claimed is: 
     
       1. A method of processing video data, comprising:
 performing a conversion between a bitstream of a video comprising one or more video regions and the video, 
 wherein a clipping parameter for filtering a reconstruction of a first video unit of a video region using a non-linear adaptive loop filter is derived based on first side information included in the bitstream and a first adaptation parameter set identification, and 
 wherein filtering coefficients for filtering the reconstruction of the first video unit using the non-linear adaptive loop filter are derived based on second side information included in the bitstream and the first adaptation parameter set identification used for deriving the clipping parameter, and 
 wherein in a case that a prediction from data information associated with the first adaptation parameter set identification is enabled for at least some of the filtering coefficients of the first video unit, the data information associated with the first adaptation parameter set identification is also used for predicting the clipping parameter, and 
 wherein a value of the clipping parameter corresponding to a first clipping index under a first bit-depth is equal to a value resulting from applying a shifting operation on another clipping parameter corresponding to the first clipping index under a second bit-depth. 
 
     
     
       2. The method of  claim 1 , wherein the first video unit is a coding tree unit, a coding tree block, or a slice. 
     
     
       3. The method of  claim 1 , wherein for a first sample in the first video unit, a first filtering index is derived based on multiple sample differences in different directions. 
     
     
       4. The method of  claim 3 , wherein the clipping parameter is derived further based on the first filtering index. 
     
     
       5. The method of  claim 4 , wherein the clipping parameter is derived further based on a bit-depth value of the first video unit. 
     
     
       6. The method of  claim 3 , wherein the first video unit is split into multiple M*M video sub-region, and the multiple sample differences in different directions are derived for every M*M video sub-region, and wherein M is equal to 2 or 4. 
     
     
       7. The method of  claim 6 , wherein the multiple sample differences in different directions are derived based on 1:N subsampling rate, wherein N is greater than 1. 
     
     
       8. The method of  claim 1 , wherein the conversion includes encoding the video into the bitstream. 
     
     
       9. The method of  claim 1 , wherein the conversion includes decoding the video from the bitstream. 
     
     
       10. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 perform a conversion between a bitstream of a video comprising one or more video regions and the video, 
 wherein a clipping parameter for filtering a reconstruction of a first video unit of a video region using a non-linear adaptive loop filter is derived based on first side information included in the bitstream and a first adaptation parameter set identification, and 
 wherein filtering coefficients for filtering the reconstruction of the first video unit using the non-linear adaptive loop filter are derived based on second side information included in the bitstream and the first adaptation parameter set identification used for deriving the clipping parameter, 
 wherein in a case that a prediction from data information associated with the first adaptation parameter set identification is enabled for at least some of the filtering coefficients of the first video unit, the data information associated with the first adaptation parameter set identification is also used for predicting the clipping parameter, and 
 wherein a value of the clipping parameter corresponding to a first clipping index under a first bit-depth is equal to a value resulting from applying a shifting operation on another clipping parameter corresponding to the first clipping index under a second bit-depth. 
 
     
     
       11. The apparatus of  claim 10 , wherein the first video unit is a coding tree unit, a coding tree block, or a slice. 
     
     
       12. The apparatus of  claim 10 , wherein for a first sample in the first video unit, a first filtering index is derived based on multiple sample differences in different directions. 
     
     
       13. The apparatus of  claim 12 , wherein the clipping parameter is derived further based on the first filtering index. 
     
     
       14. The apparatus of  claim 12 , wherein the first video unit is split into multiple M*M video sub-region, and the multiple sample differences in different directions are derived for every M*M video sub-region, and wherein M is equal to 2 or 4. 
     
     
       15. A non-transitory computer-readable storage medium storing instructions that cause a processor to:
 perform a conversion between a bitstream of a video comprising one or more video regions and the video, 
 wherein a clipping parameter for filtering a reconstruction of a first video unit of a video region using a non-linear adaptive loop filter is derived based on first side information included in the bitstream and a first adaptation parameter set identification, and 
 wherein filtering coefficients for filtering the reconstruction of the first video unit using the non-linear adaptive loop filter are derived based on second side information included in the bitstream and the first adaptation parameter set identification used for deriving the clipping parameter, 
 wherein in a case that a prediction from data information associated with the first adaptation parameter set identification is enabled for at least some of the filtering coefficients of the first video unit, the data information associated with the first adaptation parameter set identification is also used for predicting the clipping parameter, and 
 wherein a value of the clipping parameter corresponding to a first clipping index under a first bit-depth is equal to a value resulting from applying a shifting operation on another clipping parameter corresponding to the first clipping index under a second bit-depth. 
 
     
     
       16. The non-transitory computer-readable storage medium of  claim 15 , wherein for a first sample in the first video unit, a first filtering index is derived based on multiple sample differences in different directions, and
 wherein the clipping parameter is derived further based on the first filtering index. 
 
     
     
       17. The non-transitory computer-readable storage medium of  claim 15 , wherein for a first sample in the first video unit, a first filtering index is derived based on multiple sample differences in different directions, and
 wherein the clipping parameter is derived further based on the first filtering index. 
 
     
     
       18. A method for storing a bitstream of a video, wherein the method comprises:
 generating the bitstream of the video comprising one or more video regions; and 
 storing the bitstream in a non-transitory computer-readable recording medium, 
 wherein a clipping parameter for filtering a reconstruction of a first video unit of a video region using a non-linear adaptive loop filter is derived based on first side information included in the bitstream and a first adaptation parameter set identification, and 
 wherein filtering coefficients for filtering the reconstruction of the first video unit using the non-linear adaptive loop filter are derived based on second side information included in the bitstream and the first adaptation parameter set identification used for deriving the clipping parameter, 
 wherein in a case that a prediction from data information associated with the first adaptation parameter set identification is enabled for at least some of the filtering coefficients of the first video unit, the data information associated with the first adaptation parameter set identification is also used for predicting the clipping parameter, and 
 wherein a value of the clipping parameter corresponding to a first clipping index under a first bit-depth is equal to a value resulting from applying a shifting operation on another clipping parameter corresponding to the first clipping index under a second bit-depth. 
 
     
     
       19. The method of  claim 18 , wherein for a first sample in the first video unit, a first filtering index is derived based on multiple sample differences in different directions, and
 wherein the clipping parameter is derived further based on the first filtering index. 
 
     
     
       20. The method of  claim 18 , wherein for a first sample in the first video unit, a first filtering index is derived based on multiple sample differences in different directions, and
 wherein the clipping parameter is derived further based on the first filtering index.